The present invention relates to an impact tool employing an electric motor.
Impact tools driven by air motors are known in the art. An impact tool is one in which an output shaft (commonly referred to as an “anvil”) is struck by a rotating mass (commonly referred to in the art as a “hammer”). The output shaft is coupled to the fastener to be tightened or loosened, and each strike of the hammer on the anvil applies torque to the fastener. Because of the nature of impact loading compared to constant loading, an impact tool can deliver higher torque to the fastener than a constant drive fastener driver.
One known mechanism within an impact tool is the Maurer mechanism, so-named because of the original inventor of the concept, which is described in U.S. Pat. No. 3,661,217. In a typical Maurer mechanism, the hammer surrounds the anvil. The hammer backs up or rebounds in response to striking the anvil, and then resumes forward rotation. The geometric shapes of the hammer and anvil cause the hammer to cam past the anvil when the hammer resumes forward rotation, and strike the anvil on the subsequent rotation. This enables the hammer to rotate more than 360° prior to each impact with the anvil and deliver the maximum impact load to the anvil with each strike.